Polycrystalline diamond compact and method of making same

ABSTRACT

A polycrystalline diamond compact includes a substrate and a polycrystalline diamond table attached to the substrate. The polycrystalline diamond table includes an upper surface and at least one peripheral surface. Diamond grains of the polycrystalline diamond table define a plurality of interstitial regions. The polycrystalline diamond table includes a region having silicon carbide positioned within at least some of the interstitial regions thereof. In an embodiment, the first region extends over only a selected portion of the upper surface and/or at least a portion of the at least one peripheral surface. In another embodiment, the first region substantially contours the upper surface and a chamfer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/983,619 filed on 9 Nov. 2007, which claims the benefit of U.S.Provisional Application No. 60/860,098 filed on 20 Nov. 2006 and U.S.Provisional Application No. 60/876,701 filed on 21 Dec. 2006, thecontents of each of the foregoing applications are incorporated herein,in their entirety, by this reference.

BACKGROUND

Wear-resistant, superabrasive compacts are utilized for a variety ofmechanical applications. For example, polycrystalline diamond compacts(“PDCs”) are used in drilling tools (e.g., cutting elements, gagetrimmers, etc.), machining equipment, bearing apparatuses, wire-drawingmachinery, and in other mechanical systems.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller cone drill bits and fixed cutter drillbits. A PDC cutting element or cutter typically includes a superabrasivediamond layer or table. The diamond table is formed and bonded to asubstrate using an ultra-high pressure, ultra-high temperature (“HPHT”)process. The substrate is often brazed or otherwise joined to anattachment member such as a stud or a cylindrical backing. A studcarrying the PDC may be used as a PDC cutting element when mounted to abit body of a rotary drill bit by press-fitting, brazing, or otherwisesecuring the stud into a receptacle formed in the bit body. The PDCcutting element may also be brazed directly into a preformed pocket,socket, or other receptacle formed in the bit body. Generally, a rotarydrill bit may include a number of PDC cutting elements affixed to thedrill bit body.

Conventional PDCs are normally fabricated by placing a cemented carbidesubstrate into a container or cartridge with a volume of diamondparticles positioned on a surface of the cemented carbide substrate. Anumber of such cartridges may be typically loaded into an HPHT press.The substrates and volume of diamond particles are then processed underHPHT conditions in the presence of a catalyst material that causes thediamond particles to bond to one another to form a matrix of bondeddiamond grains defining a diamond table. The catalyst material is oftena solvent catalyst, such as cobalt, nickel, or iron that is used forfacilitating the intergrowth of the diamond particles.

In one conventional approach, a constituent of the cemented carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. The cobalt acts as a catalyst tofacilitate intergrowth between the diamond particles, which results information of bonded diamond grains. Often, a solvent catalyst may bemixed with the diamond particles prior to subjecting the diamondparticles and substrate to the HPHT process.

The solvent catalyst dissolves carbon from the diamond particles orportions of the diamond particles that graphitize due to the hightemperature being used in the HPHT process. The solubility of the stablediamond phase in the solvent catalyst is lower than that of themetastable graphite under HPHT conditions. As a result of thissolubility difference, the undersaturated graphite tends to dissolveinto solvent catalyst and the supersaturated diamond tends to depositonto existing diamond particles to form diamond-to-diamond bonds.Accordingly, diamond grains become mutually bonded to form a matrix ofpolycrystalline diamond with interstitial regions between the bondeddiamond grains being occupied by the solvent catalyst.

The presence of the solvent catalyst in the diamond table is believed toreduce the thermal stability of the diamond table at elevatedtemperatures. For example, the difference in thermal expansioncoefficient between the diamond grains and the solvent catalyst isbelieved to lead to chipping or cracking in the PDC during drilling orcutting operations, which consequently can degrade the mechanicalproperties of the PDC or cause failure. Additionally, some of thediamond grains can undergo a chemical breakdown or back-conversion withthe solvent catalyst. At extremely high temperatures, portions ofdiamond grains may transform to carbon monoxide, carbon dioxide,graphite, or combinations thereof, thus, degrading the mechanicalproperties of the PDC.

Therefore, manufacturers and users of superabrasive materials continueto seek improved thermally stable, superabrasive materials andprocessing techniques.

SUMMARY

Embodiments of the present invention relate to methods of fabricatingsuperabrasive articles, such as PDCs, and intermediate articles formedduring fabrication of such PDCs. Many different PDC embodimentsdisclosed herein include a thermally-stable polycrystalline diamondtable in which silicon carbide occupies a portion of the interstitialregions thereof formed between bonded diamond grains.

In one embodiment of the present invention, a method of fabricating asuperabrasive article is disclosed. A mass of unsintered diamondparticles may be infiltrated with metal-solvent catalyst from ametal-solvent-catalyst-containing material to promote formation of asintered body of diamond grains including interstitial regions. At leasta portion of the interstitial regions may also be infiltrated withsilicon from a silicon-containing material. The silicon reacts with thesintered body to form silicon carbide within a portion of theinterstitial regions.

In another embodiment of the present invention, another method offabricating a superabrasive article is disclosed. At least a portion ofinterstitial regions of a pre-sintered-polycrystalline diamond body maybe infiltrated with silicon from a silicon-containing material. At leasta portion of metal-solvent catalyst located within the at least aportion of interstitial regions of the pre-sintered-polycrystallinediamond body may be displaced into a porous mass. The silicon and thepre-sintered-polycrystalline diamond body are reacted to form siliconcarbide within the at least a portion of the interstitial regions. Asection of the polycrystalline diamond table so-formed may be removed bya suitable material-removal process so that an upper region of thepolycrystalline diamond table includes substantially only siliconcarbide within the interstitial regions thereof.

In another embodiment of the present invention, a polycrystallinediamond compact includes a substrate and a polycrystalline diamond tableattached to the substrate. The polycrystalline diamond table includingan upper surface, at least one peripheral surface, and a chamferextending between the upper surface and the peripheral surface. Diamondgrains of the polycrystalline diamond table define a plurality ofinterstitial regions. The polycrystalline diamond table includes a firstregion extending inwardly from the upper surface and the chamfer, withthe first region substantially contouring the upper surface and thechamfer. The first region includes silicon carbide positioned within atleast some of the interstitial regions thereof. The polycrystallinediamond table includes a bonding region bonded to the substrate, withthe bonding region including metal-solvent catalyst positioned within asecond portion of the interstitial regions.

In a further embodiment of the present invention, a method offabricating a polycrystalline diamond compact includes positioning an atleast partially porous polycrystalline body between a silicon-containingmaterial and a substrate that is adjacent to a metal-solvent catalyst.The at least partially porous polycrystalline body exhibits an uppersurface, at least one peripheral surface, and a chamber extendingbetween the upper surface and the at least one peripheral surface. Themethod further includes subjecting the at least partially porouspolycrystalline body, the silicon-containing material, and the substrateto an HPHT process to infiltrate a first region that extends inwardlyfrom the upper surface and the chamfer with silicon from thesilicon-containing material.

In yet another embodiment of the present invention, a polycrystallinediamond compact includes a substrate and a polycrystalline diamond tableattached to the substrate. The polycrystalline diamond table includingan upper surface. Diamond grains of the polycrystalline diamond tabledefine a plurality of interstitial regions. The polycrystalline diamondtable includes a first region including silicon carbide positionedwithin a first portion of the interstitial regions, the first regionextending over only a selected portion of the upper surface. Thepolycrystalline diamond table further includes a bonding region bondedto the substrate, with the bonding region including metal-solventcatalyst positioned within a second portion of the interstitial regions.

In still a further embodiment of the present invention, a method offabricating a polycrystalline diamond compact includes positioning an atleast partially porous polycrystalline body between a silicon-containingmaterial and a substrate adjacent to a metal-solvent catalyst. The atleast partially porous polycrystalline body includes an upper surfaceand at least one peripheral surface, with the silicon-containingmaterial extending over only a portion of the upper surface and/or atleast a portion of the at least one peripheral surface. The methodfurther includes subjecting the at least partially porouspolycrystalline body, the silicon-containing material, and the substrateto an HPHT process to infiltrate a first region of the at leastpartially porous polycrystalline body that extends along only a portionof the upper surface thereof.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the present invention,wherein like reference numerals refer to like or similar elements indifferent views or embodiments shown in the drawings.

FIG. 1A is a schematic side cross-sectional view of an assemblyincluding a substrate, a porous polycrystalline diamond body, and asilicon-containing material used to fabricate a PDC according to oneembodiment of the present invention.

FIG. 1B is a schematic side cross-sectional view of an assemblyincluding a substrate, a porous polycrystalline diamond body in which aregion remote from the substrate contains tungsten carbide, and asilicon-containing material used to fabricate a PDC according to oneembodiment of the present invention.

FIG. 2A is a schematic side cross-sectional view of the PDC resultingfrom HPHT processing of the assembly shown in FIG. 1A.

FIG. 2B is a schematic perspective view of the PDC shown in FIG. 2A.

FIG. 2C is a schematic cross-sectional view of the PDC so-formed whenthe polycrystalline diamond body shown in FIG. 1A includes a preformedchamfer according to another embodiment.

FIG. 3A is a schematic side cross-sectional view of another assemblythat may be used to form a PDC with a selectively-shaped cutting regionaccording to another embodiment of the present invention.

FIG. 3B is a schematic side cross-sectional view of another assemblythat may be used to form a PDC in which silicon infiltrates into apolycrystalline diamond body through sides thereof according to anotherembodiment of the present invention.

FIG. 4A is a schematic side cross-sectional view of the PDC resultingfrom HPHT processing of the assembly shown in FIG. 3A.

FIG. 4B is a schematic top plan view of the PDC resulting from HPHTprocessing of the assembly shown in FIG. 3A when the silicon-containingmaterial included multiple wedge-shaped portions.

FIG. 5 is a schematic side cross-sectional view of another assembly thatmay be used to form the PDC shown in FIGS. 2A and 2B according toanother embodiment of the present invention.

FIG. 6 is a schematic side cross-sectional view of another assembly thatmay be used to form the PDC shown in FIGS. 2A and 2B according to yetanother embodiment of the present invention.

FIG. 7 is a schematic side cross-sectional view of an assembly includinga substrate, unsintered diamond particles, a metal-solvent-catalystmaterial, and a silicon-containing material used to fabricate a PDCaccording to another embodiment of the present invention.

FIG. 8 is a schematic side cross-sectional view of the PDC resultingfrom HPHT processing of the assembly shown in FIG. 7.

FIG. 9 is a schematic side cross-sectional view of an assembly includinga substrate, a silicon-containing material, a diamond table, and porousmass used to fabricate a PDC according to another embodiment of thepresent invention.

FIG. 10 is a schematic side cross-sectional view of the resultingstructure formed from HPHT processing of the assembly shown in FIG. 9.

FIG. 11 is a PDC formed by removing a portion of the multi-regionstructure shown in FIG. 10.

FIG. 12 is a schematic cross-sectional view of an assembly including asubstrate, a mass of unsintered diamond particles, and layers ofmetal-solvent-catalyst-containing material and silicon-containingmaterial disposed between the substrate and the mass of unsintereddiamond particles used to fabricate a PDC according to anotherembodiment of the present invention.

FIG. 13 is a schematic side cross-sectional view of the resultingstructure from HPHT processing of the assembly shown in FIG. 12.

FIG. 14 is an isometric view of one embodiment of a rotary drill bitincluding at least one superabrasive cutting element including a PDCconfigured according to any of the various PDC embodiments of thepresent invention.

FIG. 15 is a top elevation view of the rotary drill bit of FIG. 14.

FIG. 16 is a graph showing the measured temperature versus lineardistance during a vertical turret lathe test on a conventional, leachedPDC and a PDC according to working example 2 of the present invention.

FIG. 17 is a graph showing the measured normal force versus lineardistance during a vertical turret lathe test on a conventional, leachedPDC and a PDC according to working example 2 of the present invention.

FIG. 18 is a graph illustrating the wear flat volume characteristics ofa conventional, leached PDC and a PDC according to working example 2 ofthe present invention.

DETAILED DESCRIPTION

Embodiments of the present invention relate to methods of fabricatingsuperabrasive articles, such as PDCs, and intermediate articles formedduring fabrication of such PDCs. For example, many different PDCembodiments disclosed herein include a thermally-stable polycrystallinediamond table in which silicon carbide occupies a portion of theinterstitial regions formed between bonded diamond grains. Thesuperabrasive articles disclosed herein may be used in a variety ofapplications, such as drilling tools (e.g., compacts, cutting elements,gage trimmers, etc.), machining equipment, bearing apparatuses,wire-drawing machinery, and other apparatuses. As used herein, the term“superabrasive” means a material that exhibits a hardness exceeding ahardness of tungsten carbide. For example, a superabrasive article is anarticle of manufacture, at least a portion of which exhibits a hardnessexceeding the hardness of tungsten carbide.

FIGS. 1A-2B show an embodiment of a method according to the presentinvention for fabricating a PDC and the resulting structure of the PDC.As shown in FIG. 1A, an assembly 10 includes an at least partiallyporous polycrystalline diamond body 14 (i.e., apre-sintered-polycrystalline diamond body) positioned adjacent to asubstrate 12. The assembly 10 further includes a silicon-containingmaterial 16 positioned adjacent to the polycrystalline diamond body 14on a side of the polycrystalline diamond body 14 opposite the substrate12. In one embodiment of the present invention, the silicon-containingmaterial 16 may comprise a green body of elemental silicon particles(e.g., crystalline or amorphous silicon particles) in the form of atape-casted tape that is placed adjacent to the polycrystalline diamondbody 14. In another embodiment of the present invention, thesilicon-containing material 16 may comprise a disc of silicon.

Still referring to FIG. 1A, the polycrystalline diamond body 14 includesa plurality of interstitial regions that were previously occupied bymetal-solvent catalyst. The polycrystalline diamond body 14 may befabricated by subjecting a plurality of diamond particles (e.g., diamondparticles having an average particle size between 0.5 μm to about 150μm) to an HPHT sintering process in the presence of a metal-solventcatalyst, such as cobalt, or other catalyst to facilitate intergrowthbetween the diamond particles to form a polycrystalline diamond table ofbonded diamond grains. In one embodiment of the present invention, thesintered diamond grains of the polycrystalline diamond body 14 mayexhibit an average grain size of about 20 μm or less. Thepolycrystalline diamond table so-formed may be immersed in an acid, suchas aqua-regia, a solution of 90% nitric acid/10% de-ionized water, orsubjected to another suitable process to remove at least a portion ofthe metal-solvent catalyst from the interstitial regions of thepolycrystalline diamond table.

In one embodiment of the present invention, the polycrystalline diamondtable is not formed by sintering the diamond particles on acemented-tungsten-carbide substrate or otherwise in the presence oftungsten carbide. In such an embodiment, the interstitial regions of thepolycrystalline diamond body 14 may contain no tungsten and/or tungstencarbide or insignificant amounts of tungsten and/or tungsten carbide,which can inhibit removal of the metal-solvent catalyst.

In other embodiments of the present invention, a polycrystalline diamondtable may be formed by HPHT sintering diamond particles in the presenceof tungsten carbide. For example, diamond particles may be placedadjacent to a cemented tungsten carbide substrate and/or tungstencarbide particles may be mixed with the diamond particles prior to HPHTsintering. In such an embodiment, the polycrystalline diamond tableso-formed may include tungsten and/or tungsten carbide that is swept inwith metal-solvent catalyst from the substrate or intentionally mixedwith the diamond particles during HPHT sintering process. For example,some tungsten and/or tungsten carbide from the substrate may bedissolved or otherwise transferred by the liquefied metal-solventcatalyst (e.g., cobalt from a cobalt-cemented tungsten carbidesubstrate) of the substrate that sweeps into the diamond particles. Thepolycrystalline diamond table so-formed may be separated from thesubstrate using a lapping process, a grinding process,wire-electrical-discharge machining (“wire EDM”), or another suitablematerial-removal process. The separated polycrystalline diamond tablemay be immersed in a suitable acid (e.g., a hydrochloric acid/hydrogenperoxide solution) to remove substantially all of the metal-solventcatalyst from the interstitial regions and form the polycrystallinediamond body 14. However, an indeterminate amount of tungsten and/ortungsten carbide may remain distributed throughout the polycrystallinediamond body 14 even after leaching. The presence of the tungsten and/ortungsten carbide within the polycrystalline diamond body 14 is currentlybelieved to significantly improve the abrasion resistance thereof evenafter infiltration with silicon and HPHT bonding to the substrate 12, aswill discussed in more detail below.

In a variation of the above-described embodiment in which thepolycrystalline diamond body 14 has tungsten and/or tungsten carbidedistributed therein, the polycrystalline diamond body 14 may comprise afirst portion including tungsten and/or tungsten carbide and a secondportion that is substantially free of tungsten and/or tungsten carbide.For example, a layer of metal-solvent catalyst (e.g., cobalt) may bepositioned between diamond particles and a cemented carbide substrate(e.g., cobalt-cemented tungsten carbide substrate) and subjected to HPHTconditions. During the HPHT sintering process, metal-solvent catalystfrom the layer sweeps through the diamond particles to effectintergrowth and bonding. Because the volume of the layer ofmetal-solvent catalyst is selected so that it is not sufficient to fillthe volume of all of the interstitial regions between the diamondparticles, metal-solvent catalyst from the substrate also sweeps in,which may carry or transfer tungsten and/or tungsten carbide. Thus, afirst region of the polycrystalline diamond table so-formed adjacent tothe substrate includes tungsten and/or tungsten carbide and a secondregion remote from the substrate is substantially free of tungstenand/or tungsten carbide. The volume of the layer of metal-solventcatalyst may be selected so that the second region exhibits a thicknesssubstantially greater than the second region. In this embodiment, themetal-solvent catalyst within the interstitial regions between bondeddiamond grains of the polycrystalline diamond table may be removed fromthe second region more easily. For example, the metal-solvent catalystmay be leached from the first region using a hydrochloric acid/hydrogenperoxide solution and the metal-solvent catalyst in the second regionmay be leached using a less aggressive nitric acid/hydrofluoric acidsolution. As shown in FIG. 1B, the polycrystalline diamond body 14so-formed after leaching may be oriented with the second region (shownas 14A) that is substantially free of tungsten and/or tungsten carbidepositioned adjacent to the substrate 12 in the assembly 10 and the firstregion (shown as 14B) that includes tungsten and/or tungsten carbidepositioned remote from the substrate 12 to form at least part of aworking or cutting region of a PDC that is ultimately formed afterprocessing.

Referring again to FIG. 1A, in another embodiment of the presentinvention, the polycrystalline diamond body 14 may be formed bysintering diamond particles or other particles capable of formingdiamond in response to an HPHT sintering process without a catalyst. Forexample, U.S. Pat. Nos. 7,516,804 and 7,841,428, each of which isincorporated herein, in its entirety, by this reference, disclose thatultra-dispersed diamond particles and fullerenes may be mixed withdiamond particles and HPHT sintered to form a polycrystalline diamondbody.

The substrate 12 may comprise a cemented-carbide material, such as acobalt-cemented tungsten carbide material or another suitable material.For example, nickel, iron, and alloys thereof are other metal-solventcatalysts that may comprise the substrate 12. Other materials that maycomprise the substrate 12 include, without limitation, cemented carbidesincluding titanium carbide, niobium carbide, tantalum carbide, vanadiumcarbide, and combinations of any of the preceding carbides cemented withiron, nickel, cobalt, or alloys thereof. A representative thickness forthe substrate 12 is a thickness of about 0.100 inches to at least about0.350 inches, more particularly about 0.150 inches to at least about0.300 inches, and even more particularly about 0.170 inches to at leastabout 0.290 inches.

The assembly 10 may be placed in a pressure transmitting medium, such asa refractory metal can, graphite structure, pyrophyllite or otherpressure transmitting structure, or another suitable container orsupporting element. Methods and apparatuses for sealing enclosuressuitable for holding the assembly 10 are disclosed in U.S. patentapplication Ser. No. 11/545,929, which is incorporated herein, in itsentirety, by this reference. The pressure transmitting medium, includingthe assembly 10, is subjected to an HPHT process using an ultra-highpressure press at a temperature of at least about 1000° Celsius (e.g.,about 1300° Celsius to about 1600° Celsius) and a pressure of at least40 kilobar (e.g., about 50 kilobar to about 70 kilobar) for a timesufficient to sinter the assembly 10 and form a PDC 18 as shown in FIGS.2A and 2B. Stated another way, the HPHT bonds the polycrystallinediamond body 14 to the substrate 12 and causes at least partialinfiltration of the silicon into the polycrystalline diamond body 14.The HPHT temperature may be sufficient to melt at least one constituentof the substrate 12 (e.g., cobalt, nickel, iron, or another constituent)and the silicon of the silicon-containing material 16. The PDC 18 mayexhibit other geometries than the geometry illustrated in FIGS. 2A and2B. For example, the PDC 18 may exhibit a non-cylindrical geometry.

As shown in FIGS. 2A and 2B, the HPHT sintered PDC 18 comprises apolycrystalline diamond table 15 that may include three regions: a firstregion 20, a second-intermediate region 22, and a third region 24 (i.e.,a bonding region). The first region 20 includes polycrystalline diamondwith substantially only silicon carbide formed within at least some ofthe interstitial regions between the bonded diamond grains of the firstregion 20. It is noted that the interstitial regions of at least thefirst region 20 may also include tungsten carbide when tungsten carbideis present in the polycrystalline diamond body 14, such as in theembodiment shown in FIG. 1B. During the HPHT process, silicon from thesilicon-containing material 16 liquefies and at least partiallyinfiltrates the interstitial regions of the polycrystalline diamond body14. The silicon reacts with the diamond grains of the polycrystallinediamond body 14 to form silicon carbide, which occupies at least some ofthe interstitial regions between the diamond grains and bonds to thediamond grains. Further, the amount of the silicon-containing material16 may be selected so that the silicon of the silicon-containingmaterial 16 fills a selected portion of the interstitial regions of thepolycrystalline diamond body 14.

During the HPHT process, metal-solvent catalyst from the substrate 12 oranother source also sweeps into the interstitial regions of thepolycrystalline diamond body 14 and fills some of the interstitialregions thereof, in addition to silicon carbide filling otherinterstitial regions as previously described with respect to the firstregion 20. In one embodiment of the present invention, thesecond-intermediate region 22 of the polycrystalline diamond table 15may include polycrystalline diamond with silicon carbide formed within aportion of the interstitial regions between the bonded diamond grains ofthe second-intermediate region 22 and metal-solvent catalyst (e.g.,cobalt) occupying another portion of the interstitial regions betweenthe bonded diamond grains of the second-intermediate region 22. Inanother embodiment of the present invention, substantially all of oronly a portion of the interstitial regions of the second-intermediateregion 22 may include an alloy of silicon and the metal-solventcatalyst, such as a silicon-cobalt solid solution alloy or anintermetallic compound of cobalt and silicon. In yet another embodimentof the present invention, at least some of the interstitial regions ofthe second-intermediate region 22 of the polycrystalline diamond table15 may include one or more of the following materials: silicon carbide,metal-solvent catalyst, silicon, and an alloy of silicon andmetal-solvent catalyst. The third region 24 includes polycrystallinediamond with substantially only metal-solvent catalyst (e.g., cobalt)occupying at least some of the interstitial regions between the bondeddiamond grains. The metal-solvent catalyst occupying the interstitialregions of the third region 24 is liquefied and swept into thepolycrystalline diamond body 14 from the substrate 12 or another source(e.g., a metal disk, particles, etc.) during the HPHT process. The thirdregion 24 provides a strong, metallurgical bond between the substrate 12and the polycrystalline diamond table 15 to thereby function as abonding region. It is noted that at least the first region 20 of thepolycrystalline diamond table 15 may be substantially free ofnon-silicon carbide type carbides, such as tungsten carbide, when thepolycrystalline diamond body 14 is not formed in the presence oftungsten carbide.

The PDC 18 shown in FIGS. 2A and 2B exhibits an improved thermalstability relative to a conventional PDC in which the interstitialregions of the diamond table are occupied with only cobalt or anothermetal-solvent catalyst. Additionally, the wear resistance of the PDC 18may be improved relative to a conventional PDC because the siliconcarbide phase occupying the interstitial regions of the first region 20exhibits a hardness greater than a hardness of cobalt or othermetal-solvent catalysts.

The PDC 18 may also include a chamfer along a peripheral region thereof,which may be preformed in the polycrystalline diamond body 14 (e.g., bymachining or grinding) or may be machined in the polycrystalline diamondtable 15 after formation of the PDC 18. For example, FIG. 2C is across-sectional view of the PDC 18 so-formed when the polycrystallinediamond body 14 exhibits a preformed chamfer according to anotherembodiment. In such an embodiment, at least the first region 20 and, insome cases, the second-intermediate region 22 substantially contours apreformed chamfer 25 and an upper surface 27 of the polycrystallinediamond table 15, with the chamfer 25 extending between the uppersurface 27 and at least one peripheral surface 29. As thepolycrystalline diamond table 15 had a preformed chamfer, the siliconinfiltrates into the polycrystalline diamond table 15 so that a depth“d” of the first region 20 is substantially the same when measured fromthe upper surface 27 and the chamfer 25. The depth “d” may be about 50μm to about 1000 μm, about 150 μm to about 500 μm, or about 100 μm toabout 200 μm.

Although the assembly 10 shown in FIGS. 1A and 1B includes the substrate12, in another embodiment of the present invention, the substrate 12 maybe omitted. In such an embodiment of the present invention, an assemblyof the polycrystalline diamond body 14 and the silicon-containingmaterial 16 may be subjected to an HPHT process to form apolycrystalline diamond table. After the HPHT process, a carbide layer(e.g., a tungsten carbide layer) may be deposited on the polycrystallinediamond table, as disclosed in U.S. Patent Application Publication No.20080085407, to form a PDC and enable attaching the PDC to a bit body ofa rotary drill bit. U.S. Patent Application Publication No. 20080085407is incorporated herein, in its entirety, by this reference. In anotherembodiment of the present invention, the polycrystalline diamond tablemay be brazed or otherwise secured to a bit body of a rotary drill bit.

One of ordinary skill in the art will recognize that many variations forselectively forming silicon carbide regions within apre-sintered-polycrystalline-diamond body may be employed. For example,in another embodiment of the present invention, a PDC may be formed witha polycrystalline diamond table including a cutting region exhibiting aselected configuration. The cutting region may comprise bonded diamondgrains with silicon carbide within at least some of the interstitialregions between the bonded diamond grains. By only infiltrating aselected region of an at least partially porous polycrystalline diamondbody with silicon, the toughness may be improved. As shown in FIG. 3A, asilicon-containing material 16′ in the form of body of silicon oramorphous silicon, green body of silicon particles in the form of atape-casted tape in the form of a tape-casted tape may be placedadjacent to the polycrystalline diamond body 14. For example, thesilicon-containing material 16′ may exhibit an annular geometry, awedge-shaped geometry, or another suitable geometry. A mask 21 (e.g., amica disk or other ceramic mask) may be disposed adjacent to thesilicon-containing material 16′ to cover regions of the polycrystallinediamond body 14 that are not covered by silicon-containing material 16′help prevent silicon infiltration into the masked region of thepolycrystalline diamond body 14.

As shown in FIG. 4A, upon subjecting assembly 10′ to HPHT conditions asdescribed generally hereinabove with respect to the assembly 10, a PDC18′ is formed with a polycrystalline diamond table 15′ including cuttingregion 20′ formed peripherally about intermediate region 22′ and a thirdregion 24′. The cutting region 20′ comprises bonded diamond grains withsubstantially only silicon carbide within the interstitial regionsbetween the bonded diamond grains. In one embodiment of the presentinvention, the intermediate region 22′ comprises bonded diamond grainswith silicon carbide within a portion of the interstitial regions andmetal-solvent catalyst from the substrate 12 or another source withinanother portion of the interstitial regions. In another embodiment ofthe present invention, substantially all of or only a portion of theinterstitial regions of the second-intermediate region 22′ includes analloy of silicon and metal-solvent catalyst, such as a silicon-cobaltsolid solution alloy or an intermetallic compound of cobalt and silicon.In yet another embodiment of the present invention, at least some of theinterstitial regions of the second-intermediate region 22′ of thepolycrystalline diamond table 15 may include one or more of thefollowing materials: silicon carbide, metal-solvent catalyst, silicon,and an alloy of silicon and metal-solvent catalyst. The third region 24′is formed adjacent to the substrate 12 and provides a strong,metallurgical bond between the polycrystalline diamond table 15′ and thesubstrate 12. The third region 24′ comprises bonded diamond grains withsubstantially only the metal-solvent catalyst from the substrate 12 oranother source within the interstitial regions between the bondeddiamond grains. The third region 24′ provides a tough core thatcompliments the more thermally-stable first region 20′. Depending uponthe geometry of the silicon-containing material 16′, the geometry of thecutting region 20′ of the polycrystalline diamond table 15′ may also beformed to exhibit other selected geometries.

FIG. 4B is a top plan view of the PCD table 15′ when thesilicon-containing material 16′ exhibited a wedge-shaped geometry, withmultiple wedge-shaped portions forming the cutting region 20′. Ofcourse, other geometries may be employed for the cutting region 20′ andthe intermediate region 22′ that depart from the illustrated geometryshown in FIG. 4B. For example, the cutting region 20′ and theintermediate region 22′ may exhibit an annular geometry, as describedhereinabove, or another selected geometry.

Of course, in any of the embodiments described herein that selectivelyinfiltrate the polycrystalline diamond body 14 with silicon, thepolycrystalline diamond body 14 may also be chamfered. However, thepolycrystalline diamond table 15′ may also be chamfered after beingformed.

In some embodiments, the polycrystalline diamond table 15′ may besubjected to a leaching process to deplete the third region 24′ shown inFIGS. 4A and 4B of metal-solvent catalyst (e.g., cobalt). Leaching thethird region 24′ may improve the overall thermal-stability of thepolycrystalline diamond table 15′. The metal-solvent catalyst may bedepleted from the third region 24′ to a selected depth from the uppersurface and the peripheral surface. For example, the leach depth may beabout 50 μm to about 1000 μm, about 150 μm to about 500 μm, or about 100μm to about 200 μm. The leaching may be performed to removesubstantially all of the metal-solvent catalyst from the third region24′.

FIG. 3B shows another embodiment of the present invention in which asilicon-containing material 16″ may be positioned adjacent to at leastone peripheral surface 17 of the polycrystalline diamond body 14. HPHTprocessing causes silicon from the silicon-containing material 16″ to atleast partially or substantially infiltrate the polycrystalline diamondbody 14. For example, the silicon from the silicon-containing material16″ may partially infiltrate the polycrystalline diamond body 14 to forma PDC including a multi-region polycrystalline diamond table.

As shown in FIG. 5, in another embodiment of the present invention, thePDC 18 may be formed by subjecting an assembly 21 to HPHT conditionssimilar to that employed on the assembly 10. The assembly 21 includes asilicon-containing material 16 positioned adjacent to a substrate 12,and between the substrate 12 and a polycrystalline diamond body 14.During HPHT processing, the assembly 21 is heated at a sufficient rateso that the metal-solvent catalyst (e.g., cobalt) and the silicon in thesilicon-containing material 16 are in a liquid state at substantiallythe same time. Such heating may cause the molten, metal-solvent catalyst(e.g., from the substrate 12, metal-solvent catalyst mixed with thesilicon-containing material 16, or another source) to occupy a portionof the interstitial regions of the polycrystalline diamond body 14 andmay cause the molten silicon to occupy other portions of theinterstitial regions of the polycrystalline diamond body 14. Uponcooling, the resultant, as-sintered PDC may exhibit a similarmulti-region diamond table as the polycrystalline diamond table 15 shownin FIGS. 2A and 2B.

FIG. 6 shows another embodiment of the present invention in which a PDC13 including a leached polycrystalline diamond table 19 and asilicon-containing material 16 are assembled and HPHT processed usingHPHT conditions as described generally hereinabove with respect to theassembly 10. In this embodiment, the PDC 13 may be formed from aconventional PDC with a polycrystalline diamond table that comprisesbonded diamond grains with cobalt or another metal-solvent catalystoccupying the interstitial regions between the bonded diamond grains.The metal-solvent catalyst may be substantially removed from thepolycrystalline diamond table by leaching using an acid, such asaqua-regia, a solution of 90% nitric acid/10% de-ionized water, oranother suitable process to remove at least a portion of themetal-solvent catalyst from the interstitial regions of thepolycrystalline diamond table. After removal of the metal-solventcatalyst from the PDC 13, a silicon-containing material 16 may bepositioned adjacent to the leached polycrystalline diamond table 19 on aside thereof opposite the substrate 12. The leached polycrystallinediamond table 19 and the silicon-containing material 16 are subjected toan HPHT process to infiltrate the leached polycrystalline diamond table19 with silicon from the silicon-containing material 16 to form a PDChaving a polycrystalline diamond table with the same or similarconstruction as the polycrystalline diamond table 15 shown in FIGS. 2Aand 2B.

FIGS. 7 and 8 show another embodiment of a method according to thepresent invention for forming a PDC. As shown in FIG. 7, an assembly 24includes a mass of unsintered diamond particles 28 positioned adjacentto the substrate 12. The mass of unsintered diamond particles 28 may bea green body of diamond particles 28 in the form of a tape-casted tape.In one embodiment of the present invention, the diamond particles 28 mayexhibit an average particle size of about 20 μm or less. In anotherembodiment of the present invention, the diamond particles 28 mayexhibit an average particle size of about 5 μm to about 50 μm. The massof unsintered diamond particles 28 may exhibit a thickness, for example,of about 0.150 inches to about 0.200 inches. The assembly 24 furtherincludes a metal-solvent-catalyst-containing material 26 positionedadjacent to the mass of diamond particles 28, and a silicon-containingmaterial 16 positioned adjacent to the metal-solvent-catalyst-containingmaterial 26. The metal-solvent-catalyst-containing material 26 mayinclude or may be formed from a material, such as cobalt, nickel, iron,or alloys thereof. The metal-solvent-catalyst-containing material 26 mayalso be a green body of metal-solvent-catalyst particles in the form ofa tape-casted tape, a thin disc of metal-solvent-catalyst material, orany other suitable metal-solvent-catalyst material or structure, withoutlimitation.

The assembly 24 may be subjected to an HPHT sintering process using HPHTprocess conditions similar to those previously discussed to form a PDC42 shown in FIG. 8. During HPHT sintering, the metal-solvent catalyst ofthe metal-solvent-catalyst-containing material 26 melts and infiltratesthe diamond particles 28 to effect intergrowth between the diamondparticles 28. Molten silicon from the silicon-containing material 16also infiltrates the diamond particles 28 and the infiltration by themolten silicon follows the infiltration of the metal-solvent catalyst.Thus, the metal-solvent catalyst from themetal-solvent-catalyst-containing material 26 promotes bonding of thediamond particles 28 to form polycrystalline diamond and the siliconinfiltrates the polycrystalline diamond so-formed. The silicon reactswith the diamond grains of the polycrystalline diamond to form siliconcarbide within some of the interstitial regions between the bondeddiamond grains. The amount of the silicon-containing material 16metal-solvent-catalyst-containing material 26 may be selected so thatthe silicon of the silicon-containing material 16 and the metal-solventcatalyst from the metal-solvent-catalyst-containing material 26,respectively, only fill a portion of the interstitial regions of thepolycrystalline diamond formed during the HPHT process.

As shown in FIG. 8, the PDC 42 formed by HPHT sintering the assembly 24includes a multi-region polycrystalline diamond table 35 similar inconfiguration to the polycrystalline diamond table 15 shown in FIGS. 2Aand 2B. The polycrystalline diamond table 35 includes: a first region36, a second-intermediate region 38, and a third region 40. The firstregion 36 includes substantially only silicon carbide within at leastsome of the interstitial regions between the bonded diamond grains. Inone embodiment of the present invention, the second-intermediate region38 may include silicon carbide within a portion of the interstitialregions between the bonded diamond grains, along with metal-solventcatalyst from the metal-solvent-catalyst-containing material 26 and/orthe substrate 12 within other portions of the interstitial regions ofthe second-intermediate region 38. In another embodiment of the presentinvention, substantially all of or only a portion of the interstitialregions of the second-intermediate region 38 may include an alloy ofsilicon and metal-solvent catalyst, such as a silicon-cobalt solidsolution alloy or an intermetallic compound of cobalt and silicon. Inyet another embodiment of the present invention, at least some of theinterstitial regions of the second-intermediate region 38 may includeone or more of the following materials: silicon carbide, metal-solventcatalyst, silicon, and an alloy of silicon and metal-solvent catalyst.The third region 40, adjacent to the substrate 12, includessubstantially only metal-solvent catalyst from the substrate 12 oranother source within the interstitial regions thereof for forming astrong, metallurgical bond between the polycrystalline diamond table 35and the substrate 12.

FIGS. 9-11 show yet another embodiment of a method according to thepresent invention for forming a PDC. As shown in FIG. 9, an assembly 44is formed by positioning a silicon-containing material 16 between asubstrate 12 and a pre-sintered-polycrystalline diamond table 46. Thepolycrystalline diamond table 46 may exhibit a thickness of, forexample, about 0.090 inches and an average grain size of about 20 μm orless. The polycrystalline diamond table 46 comprises bonded diamondgrains sintered using a metal-solvent catalyst, such as cobalt, nickel,iron, or alloys thereof. Accordingly, the polycrystalline diamond table46 includes bonded diamond grains with the metal-solvent catalystoccupying interstitial regions between the bonded diamond grains. In oneembodiment of the present invention, the polycrystalline diamond table46 may not be formed by sintering diamond particles in the presence oftungsten carbide so that the interstitial regions of the polycrystallinediamond table 46 contain no tungsten and/or tungsten carbide orinsignificant amounts of tungsten and/or tungsten carbide. In otherembodiments of the present invention, a portion or substantially theentire polycrystalline diamond table 46 may be formed to includetungsten and/or tungsten carbide distributed therethrough, as previouslydescribed with respect to the polycrystalline diamond body 14 shown inFIGS. 1A and 1B. For example, a first region of the polycrystallinediamond table 46 that is substantially free of tungsten and/or tungstencarbide may be positioned adjacent to the silicon-containing material16, while a second region of the polycrystalline diamond table 46 thatincludes tungsten and/or tungsten carbide may be positioned remote fromthe silicon-containing material 16. The assembly 44 further includes aporous mass 48 positioned adjacent to the polycrystalline diamond table46 on a side of the polycrystalline diamond table 46 opposite thesilicon-containing material 16. The porous mass 48 may be unsintereddiamond particles, unsintered aluminum oxide particles, unsinteredsilicon carbide particles, or another suitable porous mass. The porousmass 48 may also be a green body of diamond particles in the form of atape-casted tape, or any other form, without limitation.

The assembly 44 may be subjected to an HPHT sintering process usingsintering conditions similar to the sintering conditions employed on theassembly 10 to bond the various components of the assembly 44 togetherand to form a polycrystalline diamond structure 50 shown in FIG. 10.During sintering, silicon from the silicon-containing material 16 meltsand displaces all or a portion of the metal-solvent catalyst of thepolycrystalline diamond table 46 into the porous mass 48. Depending onthe sintering temperature, the metal-solvent catalyst of thepolycrystalline diamond table 46 may also be partially or completedmolten at the same time as the silicon from the silicon-containingmaterial 16. In one embodiment of the present invention, the amount ofsilicon-containing material 16 is selected so that substantially all ofthe metal-solvent catalyst of the polycrystalline diamond table 46 isdisplaced into the porous mass 48. In another embodiment of the presentinvention, the amount of the silicon-containing material 16 may beselected so that the silicon from the silicon-containing material 16displaces only a portion of the metal-solvent catalyst of thepolycrystalline diamond table 46. The silicon reacts with the diamondgrains of the polycrystalline diamond table 46 or another carbon sourceto form silicon carbide within interstitial regions between the bondeddiamond grains of the polycrystalline diamond table 46. Additionally,metal-solvent catalyst from the substrate 12 or another source alsomelts and infiltrates into a region of the polycrystalline diamond table46 adjacent the substrate 12.

As shown in FIG. 10, the polycrystalline diamond structure 50 formed byHPHT processing of the assembly 44 comprises a multi-regionpolycrystalline diamond table 55 that may include: a first region 52, asecond region 54, a third region 56, a fourth region 58, and a fifthregion 60. The first region 52 includes the particles from the porousmass 48 with at least some of the interstitial regions thereof occupiedby substantially only the metal-solvent catalyst displaced from thepolycrystalline diamond table 46. The second region 54 includes theparticles from the porous mass 48 with at least some of the interstitialregions thereof occupied by an alloy of silicon and metal-solventcatalyst, such as a silicon-cobalt solid solution alloy or anintermetallic compound of cobalt and silicon. Depending upon the amountof the silicon-containing material 16 employed, the second region 54 mayalso extend into the HPHT processed polycrystalline diamond table 46.The third region 56, fourth region 58, and fifth region 60 may be formedfrom the HPHT processed polycrystalline diamond table 46, which exhibitsa reduced thickness due to the HPHT processing. The third region 56includes polycrystalline diamond with substantially only silicon carbidewithin at least some of the interstitial regions between the bondeddiamond grains. In one embodiment of the present invention, the fourthregion 58 includes polycrystalline diamond with at least some of theinterstitial regions thereof occupied by an alloy of silicon andmetal-solvent catalyst, such as a silicon-cobalt solid solution alloy oran intermetallic compound of cobalt and silicon. In another embodimentof the present invention, the fourth region 58 may includepolycrystalline diamond with silicon carbide formed within a portion ofthe interstitial regions between the bonded diamond grains of the fourthregion 58 and metal-solvent catalyst (e.g., cobalt) occupying anotherportion of the interstitial regions between the bonded diamond grains ofthe fourth region 58. In yet another embodiment of the presentinvention, at least some of the interstitial regions of the fourthregion 58 may include one or more of the following materials: siliconcarbide, metal-solvent catalyst, silicon, and an alloy of silicon andmetal-solvent catalyst. The fifth region 60, adjacent to the substrate12, includes substantially only metal-solvent catalyst from thesubstrate 12 within at least some of the interstitial regions betweenbonded diamond grains for forming a strong, metallurgical bond betweenthe multi-region polycrystalline diamond table 55 and the substrate 12.

As shown in FIG. 11, after forming the polycrystalline diamond structure50, a PDC 63 including a multi-region structure 65 similar inconfiguration to the polycrystalline diamond table 15 shown in FIGS. 2Aand 2B may be formed by removing the first region 52 and the secondregion 54 of the multi-region structure 65 using a lapping process, agrinding process, wire EDM, or another suitable material-removalprocess.

FIGS. 12 and 13 show yet another embodiment of a method according to thepresent invention for forming a PDC. As shown in FIG. 12, an assembly 59includes a mass of unsintered diamond particles 62 with asilicon-containing material 16 and a metal-solvent catalyst-containingmaterial 26 positioned between the mass of unsintered diamond particles62 and a substrate 12. The metal-solvent-catalyst-containing material 26is positioned adjacent to the mass of unsintered diamond particles 62and the silicon-containing material 16 is positioned adjacent to thesubstrate 12. The assembly 59 may be subjected to an HPHT sinteringprocess using sintering conditions similar to the sintering conditionsemployed on the assembly 10 to form a polycrystalline diamond structure61 shown in FIG. 13. During HPHT sintering, the silicon-containingmaterial 16 and the metal-solvent catalyst-containing material 26 aremelted, and metal-solvent catalyst from themetal-solvent-catalyst-containing material 26 infiltrates the mass ofunsintered diamond particles 62 to promote bonding between the diamondparticles, thus, forming polycrystalline diamond that comprises bondeddiamond grains with interstitial regions between the bonded diamondgrains. The silicon from the silicon-containing material 16 follows theinfiltration of the mass 62 by the metal-solvent-catalyst-containingmaterial 26 and infiltrates the polycrystalline diamond so-formed. Thesilicon reacts with the diamond grains to form silicon carbide withinsome of the interstitial regions.

As shown in FIG. 13, the polycrystalline diamond structure 61 formed byHPHT sintering of the assembly 59 comprises a multi-regionpolycrystalline diamond table 69 that may include: a first region 64, asecond region 65, a third region 66, a fourth region 67, and a fifthregion 68. The first region 64 includes polycrystalline diamond with atleast some of the interstitial regions thereof occupied by substantiallyonly the metal-solvent catalyst from themetal-solvent-catalyst-containing material 26. In one embodiment of thepresent invention, the second region 65 includes polycrystalline diamondwith at least some of the interstitial regions thereof occupied by analloy of silicon and metal-solvent catalyst, such as a silicon-cobaltsolid solution alloy or an intermetallic compound of cobalt and silicon.In another embodiment of the present invention, the second region 65 mayinclude polycrystalline diamond with silicon carbide formed within aportion of the interstitial regions between the bonded diamond grains ofthe second region 65 and metal-solvent catalyst (e.g., cobalt) occupyinganother portion of the interstitial regions between the bonded diamondgrains of the second region 65. In yet another embodiment of the presentinvention, at least some of the interstitial regions of the secondregion 65 may include one or more of the following materials: siliconcarbide, metal-solvent catalyst, silicon, and an alloy of silicon andmetal-solvent catalyst. The third region 66 includes polycrystallinediamond with substantially only silicon carbide within at least some ofthe interstitial regions thereof. The fourth region 67 may include acomposition and microstructure that is the same or similar to the secondregion 65. The fifth region 68 adjacent to the substrate 12 includessubstantially only metal-solvent catalyst from the substrate 12 oranother source within the interstitial regions thereof for forming astrong, metallurgical bond between the multi-region polycrystallinediamond table 69 and the substrate 12. After forming the multi-regionpolycrystalline diamond table 69, a PDC including a polycrystallinediamond table similar in configuration to the polycrystalline diamondtable 15 shown in FIGS. 2A and 2B may be formed by removing the firstregion 64 and the second region 65 using a lapping process, a grindingprocess, wire EDM, or another suitable material-removal process.

In the embodiments described above, silicon is introduced into apolycrystalline diamond table by infiltrating molten silicon. However,it is contemplated that silicon may be introduced in vapor form such asvia chemical vapor deposition or another suitable vapor depositionprocess. Additionally, a polycrystalline diamond table that has beenintegrally formed with a cemented carbide substrate and leached to aselected depth from an upper surface thereof may also benefit from beinginfiltrated with silicon in molten or vapor form to form a morethermally-stable polycrystalline diamond table.

FIGS. 14 and 15 show an isometric view and a top elevation view,respectively, of a rotary drill bit 70 according to one embodiment ofthe present invention. The rotary drill bit 70 includes at least one PDCconfigured according to any of the previously described PDC embodiments.The rotary drill bit 70 comprises a bit body 72 that includes radiallyand longitudinally extending blades 74 with leading faces 76, and athreaded pin connection 78 for connecting the bit body 72 to a drillingstring. The bit body 72 defines a leading end structure for drillinginto a subterranean formation by rotation about a longitudinal axis 80and application of weight-on-bit. At least one PDC, fabricated accordingto any of the previously described PDC embodiments, may be affixed torotary drill bit 70. As best shown in FIG. 15, a plurality of PDCs 86are secured to the blades 74. For example, each PDC 86 may include apolycrystalline diamond table 88 bonded to a substrate 90. Moregenerally, the PDCs 86 may comprise any PDC disclosed herein, withoutlimitation. In addition, if desired, in some embodiments of the presentinvention, a number of the PDCs 86 may be conventional in construction.Also, circumferentially adjacent blades 74 define so-called junk slots82 therebetween, as known in the art. Additionally, the rotary drill bit70 includes a plurality of nozzle cavities 84 for communicating drillingfluid from the interior of the rotary drill bit 70 to the PDCs 86.

FIGS. 14 and 15 merely depict one embodiment of a rotary drill bit thatemploys at least one cutting element that comprises a PDC fabricated andstructured in accordance with the disclosed embodiments, withoutlimitation. The rotary drill bit 70 is used to represent any number ofearth-boring tools or drilling tools, including, for example, core bits,roller-cone bits, fixed-cutter bits, eccentric bits, bicenter bits,reamers, reamer wings, or any other downhole tool including PDCs,without limitation.

The PDCs disclosed herein may also be utilized in applications otherthan cutting technology. The disclosed PDC embodiments may be used inwire dies, bearings, artificial joints, inserts, cutting elements, andheat sinks. Thus, any of the PDCs disclosed herein may be employed in anarticle of manufacture including at least one superabrasive element orcompact.

Thus, the embodiments of PDCs disclosed herein may be used on anyapparatus or structure in which at least one conventional PDC istypically used. For example, in one embodiment of the present invention,a rotor and a stator (i.e., a thrust bearing apparatus) may each includea PDC according to any of the embodiments disclosed herein and may beoperably assembled to a downhole drilling assembly. U.S. Pat. Nos.4,410,054; 4,560,014; 5,364,192; 5,368,398; and 5,480,233, thedisclosure of each of which is incorporated herein, in its entirety, bythis reference, disclose subterranean drilling systems within whichbearing apparatuses utilizing PDCs disclosed herein may be incorporated.The embodiments of PDCs disclosed herein may also form all or part ofheat sinks, wire dies, bearing elements, cutting elements, cuttinginserts (e.g., on a roller cone type drill bit), machining inserts, orany other article of manufacture as known in the art. Other examples ofarticles of manufacture that may use any of the PDCs disclosed hereinare disclosed in U.S. Pat. Nos. 4,811,801; 4,268,276; 4,468,138;4,738,322; 4,913,247; 5,016,718; 5,092,687; 5,120,327; 5,135,061;5,154,245; 5,460,233; 5,544,713; and 6,793,681, the disclosure of eachof which is incorporated herein, in its entirety, by this reference.

The following working examples of the present invention set forthvarious formulations for forming PDCs. The following working examplesprovide further detail in connection with the specific embodimentsdescribed above.

Comparative Working Example 1

A conventional PDC was formed from a mixture of diamond particles havingan average grain size of about 18 μm. The mixture was placed adjacent toa cobalt-cemented tungsten carbide substrate. The mixture and substratewere placed in a niobium can and HPHT sintered at a temperature of about1400° Celsius and a pressure of about 5 GPa to about 8 GPa for about 90seconds to form the conventional PDC. The conventional PDC wasacid-leached to a depth of about 70 μm to remove substantially all ofthe cobalt from a region of the polycrystalline diamond table. Thethickness of the polycrystalline diamond table of the PDC was 0.090inches and a 0.012 inch chamfer was machined in the polycrystallinediamond table. The thermal stability of the conventional PDC so-formedwas evaluated by measuring the distance cut in a Sierra White graniteworkpiece prior to failure without using coolant in a vertical turretlathe test. The distance cut is considered representative of the thermalstability of the PDC. The conventional PDC was able to cut a distance ofabout only 2000 linear feet in the workpiece prior to failure. Evidenceof failure of the conventional PDC is best shown in FIG. 16 where themeasured temperature of the conventional PDC during cutting increaseddramatically at around about 2000 linear feet and in FIG. 17 where thenormal force required to continue cutting also increased dramatically ataround about 2000 linear feet.

Working Example 2

A PDC was formed by first fabricating a leached polycrystalline diamondbody. The leached polycrystalline diamond body was formed by HPHTsintering diamond particles having an average grain size of about 18 μmin the presence of cobalt. The sintered-polycrystalline-diamond bodyincluded cobalt within the interstitial regions between bonded diamondgrains. The sintered-polycrystalline-diamond body was leached using asolution of 90% nitric acid/10% de-ionized water for a time sufficientto remove substantially all of the cobalt from the interstitial regionsto form the leached polycrystalline diamond body. The leachedpolycrystalline diamond body was placed adjacent to a cobalt-cementedtungsten carbide substrate. A green layer of silicon particles wasplaced adjacent to the leached polycrystalline diamond body on a sidethereof opposite the cobalt-cemented tungsten carbide substrate. Theleached polycrystalline diamond body, cobalt-cemented tungsten carbidesubstrate, and green layer of silicon particles were placed within aniobium can, and HPHT sintered at a temperature of about 1400° Celsiusand a pressure of about 5 GPa to about 7 GPa for about 60 seconds toform a PDC that exhibited a similar multi-region diamond table as thepolycrystalline diamond table 15 shown in FIGS. 2A and 2B, with siliconcarbide formed in a portion of the interstitial regions between thebonded diamond grains. The thickness of the polycrystalline diamondtable was about 0.090 inches and a chamfer of about 0.01065 inch wasmachined in the polycrystalline diamond table.

The thermal stability of the PDC of example 2 was evaluated by measuringthe distance cut in a Sierra White granite workpiece without usingcoolant in a vertical turret lathe test. The PDC of example 2 was ableto cut a distance of over 14000 linear feet in a granite workpiecewithout failing and without using coolant. This is best shown in FIGS.16 and 17 where the measured temperature (FIG. 16) of the PDC of example2 during cutting of the workpiece and the normal force required tocontinue cutting the workpiece (FIG. 17) does not increase dramaticallyas occurred with the conventional PDC of comparative example 1 duringcutting. Therefore, thermal stability tests indicate that the PDC ofexample 2 exhibited a significantly improved thermal stability comparedto the conventional PDC of comparative example 1.

The wear resistance of the PDCs of comparative example 1 and example 2were evaluated by measuring the volume of the PDC removed versus thevolume of a Sierra White granite workpiece removed in a vertical turretlathe with water used as a coolant. As shown in FIG. 18, the wearflatvolume tests indicated that the PDC of example 2 exhibited a slightlydecreased wear resistance compared to the wear resistance of the PDC ofcomparative example 1. However, the wear resistance of the PDC ofexample 2 is still more than sufficient to function as a PDC forsubterranean drilling applications. Drop-weight tests also indicatedthat a PDC fabricated according to example 2 exhibits an impactresistance similar to a conventionally fabricated PDC, such as thecomparative example 1. Therefore, the PDC of example 2 exhibited asignificantly superior thermal stability compared to the conventionalPDC of comparative example 1 without significantly compromising wearresistance and impact resistance.

Although the present invention has been disclosed and described by wayof some embodiments, it is apparent to those skilled in the art thatseveral modifications to the described embodiments, as well as otherembodiments of the present invention are possible without departing fromthe spirit and scope of the present invention. Additionally, the words“including” and “having,” as used herein, including the claims, shall beopen ended and have the same meaning as the word “comprising.”

The invention claimed is:
 1. A polycrystalline diamond compact,comprising: a substrate; and a polycrystalline diamond table attached tothe substrate, the polycrystalline diamond table including an uppersurface, at least one peripheral surface, and a preformed chamferextending between the upper surface and the peripheral surface, diamondgrains of the polycrystalline diamond table defining a plurality ofinterstitial regions, the polycrystalline diamond table including: afirst region extending inwardly from the upper surface and the preformedchamfer, the first region substantially contouring the upper surface andthe preformed chamfer, the first region extending inwardly a depthmeasured inwardly from the upper surface that is substantially the sameas a depth measured inwardly from and along substantially an entirecross-sectional length of the preformed chamfer, the first regionincluding silicon carbide positioned within at least some of theinterstitial regions thereof; and a bonding region bonded to thesubstrate, the bonding region including metal-solvent catalystpositioned within a second portion of the interstitial regions.
 2. Thepolycrystalline diamond compact of claim 1 wherein the first region isconfigured as an annular region that extends peripherally about aportion of the bonding region.
 3. The polycrystalline diamond compact ofclaim 1 wherein the first region is extends along only a selectedportion of the upper surface.
 4. The polycrystalline diamond compact ofclaim 1 wherein the first region of the polycrystalline diamond table issubstantially free of tungsten carbide.
 5. The polycrystalline diamondcompact of claim 1 wherein the polycrystalline diamond table comprisestungsten carbide.
 6. The polycrystalline diamond compact of claim 1wherein the diamond grains of the polycrystalline diamond table exhibitan average grain size of about 20 μm or less.
 7. The polycrystallinediamond compact of claim 1 wherein the substrate comprises a cementedcarbide material.
 8. The polycrystalline diamond compact of claim 1wherein the metal-solvent catalyst comprises cobalt, iron, nickel, oralloys thereof.
 9. A rotary drill bit including a bit body adapted toengage a subterranean formation during drilling and at least onesuperabrasive cutting element affixed to the bit body, wherein the atleast one superabrasive cutting element comprises the polycrystallinediamond compact according to claim 1.